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Cell type- and differentiation stage-dependent expression of PML domains in rat, detected by monoclonal antibody
1Department of Biochemistry, University of Hong Kong, Hong Kong.
Abstract:
Using mouse monoclonal antibody (mAb) HIS55, we identified a nuclear antigen (ag) that exhibited a staining pattern of discrete foci. Such foci could be detected in cells of many mammalian species. These nuclear foci were not associated with nuclear membrane, nucleoli, or mitotic chromosomes. In isolated rat liver nuclei, HeLa cells, and normal human and rat lymph nodes, staining of HIS55 colocalized with that of 5E10. 5E10 recognizes PML nuclear domains, multimolecular complexes of unknown function containing the product of PML gene and at least two other components. HIS55 foci were expressed widely in many tissues but the expression level varied in a cell type-specific manner, with the number of HIS55 nuclear foci ranging from 0 (as in neurons) to over 100 (as in megakaryocytes) and the size ranging from fine (as in cortical thymocytes) to very large (as in urethra epithelium). HIS55 ag expression level also varied among cells of the same lineage, as observed in embryonic development of rat and in the hemopoietic system of adult rat. The expression level of HIS55 foci roughly correlated with the overall rate of protein synthesis of cells, supporting a role of PML domains as transcription regulatory units. The expression of HIS55 foci, however, did not correlate with the growth index of cell populations. Our observations on normal tissues agreed with the hypothesis that PML domain expression is regulated by external, possibly site-dependent factors. We further supported this by demonstrating that PML domains in rat ventral prostate epithelia were upregulated upon castration.
Insights
A novel nuclear antigen detected by antibody HIS55 localizes to PML nuclear domains across mammalian species. Its expression varies by cell type and correlates with protein synthesis, suggesting a role in transcription regulation.
Area of Science:
- Cell Biology
- Molecular Biology
- Immunology
Background:
- PML nuclear domains are multimolecular complexes of unknown function.
- The antibody HIS55 identifies a nuclear antigen.
- These nuclear foci are present in various mammalian cells.
Purpose of the Study:
- To characterize a novel nuclear antigen identified by monoclonal antibody (mAb) HIS55.
- To determine the localization and expression patterns of this antigen.
- To investigate the relationship between the antigen's expression and cellular functions.
Main Methods:
- Immunohistochemistry using monoclonal antibody (mAb) HIS55.
- Colocalization studies with antibody 5E10, which recognizes PML nuclear domains.
- Analysis of antigen expression in various tissues and cell types across mammalian species.
Main Results:
- HIS55 identified a nuclear antigen forming discrete foci in cells of many mammalian species.
- HIS55 staining colocalized with 5E10, indicating association with PML nuclear domains.
- Expression levels varied significantly across cell types and tissues, correlating with protein synthesis rates but not growth index.
- PML domain expression was upregulated in rat ventral prostate epithelia upon castration.
Conclusions:
- The nuclear antigen recognized by HIS55 is a component of PML nuclear domains.
- PML domain expression is regulated by cell-type-specific and external factors.
- PML domains may function as transcription regulatory units, influenced by cellular protein synthesis rates.